This disclosure is directed to polycarbonate compositions, articles formed therefrom, and their methods of manufacture, and in particular low smoke density, low heat release polycarbonate compositions, articles formed therefrom, and their methods of manufacture.
Polycarbonates are useful in a wide variety of applications at least in part because of their good balance of properties, such as moldability, heat resistance and impact properties, among others. However, polycarbonates generate smoke and heat upon burning, which makes them less suitable for applications in mass transportation (aircraft, trains, and ships), as well as in building and construction. Recently, the European Union has approved the introduction of a new harmonized fire standard for rail applications, namely EN-45545, to replace all currently active different standards in each member state, which will become fully active within the next two to three years. This standard will impose stringent requirements on smoke density and heat release properties allowed for materials used in rail interior applications. Smoke density (Ds-4) in EN-45545 is the smoke density after 4 minutes determined in accordance with ISO 5659-2, and heat release in EN-45545 is the maximum average rate of heat emission (MAHRE) determined in accordance with ISO 5660-1.
It is exceptionally challenging to develop materials that meet stringent smoke density standards in addition to other material requirements. It is particularly challenging to develop materials that meet these requirements and that have good mechanical properties and processability. Accordingly, there remains a need in the art for polycarbonate compositions that have excellent low smoke or low heat release properties. It would be a further advantage if the compositions could be rendered low smoke or low heat release without a significant detrimental effect on one or more of material cost, processability, and mechanical properties. It would be a still further advantage if the materials could be readily thermoformed or injection molded.